/* trees.c -- output deflated data using Huffman coding
 * Copyright (C) 1995-2003 Jean-loup Gailly
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

/*
 *  ALGORITHM
 *
 *      The "deflation" process uses several Huffman trees. The more
 *      common source values are represented by shorter bit sequences.
 *
 *      Each code tree is stored in a compressed form which is itself
 * a Huffman encoding of the lengths of all the code strings (in
 * ascending order by source values).  The actual code strings are
 * reconstructed from the lengths in the inflate process, as described
 * in the deflate specification.
 *
 *  REFERENCES
 *
 *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification".
 *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc
 *
 *      Storer, James A.
 *          Data Compression:  Methods and Theory, pp. 49-50.
 *          Computer Science Press, 1988.  ISBN 0-7167-8156-5.
 *
 *      Sedgewick, R.
 *          Algorithms, p290.
 *          Addison-Wesley, 1983. ISBN 0-201-06672-6.
 */

/* @(#) $Id: trees.c,v 1.1 2005/11/23 14:29:59 stingerx Exp $ */

#include "deflate.h"


/* ===========================================================================
 * Constants
 */

#define MAX_BL_BITS 7
#define END_BLOCK 256
#define REP_3_6      16
#define REPZ_3_10    17
#define REPZ_11_138  18

static const int extra_lbits[LENGTH_CODES] =
{
  0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0
};

static const int extra_dbits[D_CODES] =
{
  0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13
};

static const int extra_blbits[BL_CODES] =
{
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 3, 7
};

static const BYTE bl_order[BL_CODES] =
{
  16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
};

/* The lengths of the bit length codes are sent in order of decreasing
 * probability, to avoid transmitting the lengths for unused bit length codes.
 */

#define Buf_size (8 * 2*sizeof(char))
/* Number of bits used within bi_buf. (bi_buf might be implemented on
 * more than 16 bits on some systems.)
 */

/* ===========================================================================
 * static data. These are initialized only once.
 */

#define DIST_CODE_LEN  512 /* see definition of array dist_code below */

#include "trees.h"

struct static_tree_desc_s
{
  const ct_data *static_tree; /* static tree or NULL */
  const intf *extra_bits; /* extra bits for each code or NULL */
  int extra_base; /* base index for extra_bits */
  int elems; /* max number of elements in the tree */
  int max_length; /* max bit length for the codes */
};

static static_tree_desc static_l_desc =
{
  static_ltree, extra_lbits, LITERALS + 1, L_CODES, MAX_BITS
};

static static_tree_desc static_d_desc =
{
  static_dtree, extra_dbits, 0, D_CODES, MAX_BITS
};

static static_tree_desc static_bl_desc =
{
  (const ct_data*)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS
};

/* ===========================================================================
 * Local (static) routines in this file.
 */

static void tr_static_init(void);

static void init_block(deflate_state *s);

static void pqdownheap OF((deflate_state *s, ct_data *tree, int k));

static void gen_bitlen OF((deflate_state *s, tree_desc *desc));

static void gen_codes OF((ct_data *tree, int max_code, WORD *bl_count));

static void build_tree OF((deflate_state *s, tree_desc *desc));

static void scan_tree OF((deflate_state *s, ct_data *tree, int max_code));

static void send_tree OF((deflate_state *s, ct_data *tree, int max_code));

static int build_bl_tree OF((deflate_state *s));

static void send_all_trees OF((deflate_state *s, int lcodes, int dcodes, int blcodes));

static void compress_block OF((deflate_state *s, ct_data *ltree, ct_data *dtree));

static void set_data_type OF((deflate_state *s));

static DWORD bi_reverse OF((DWORD value, int length));

static void bi_windup OF((deflate_state *s));

static void bi_flush OF((deflate_state *s));

static void copy_block OF((deflate_state *s, BYTE *buf, DWORD len, int header));

#define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)

/* Send a code of the given tree. c and tree must not have side effects */


/* ===========================================================================
 * Output a short LSB first on the stream.
 * IN assertion: there is enough room in pendingBuf.
 */

#define put_short(s, w) { put_byte(s, (BYTE)((w) & 0xff)); put_byte(s, (BYTE)((WORD)(w) >> 8)); }

/* ===========================================================================
 * Send a value on a given number of bits.
 * IN assertion: length <= 16 and value fits in length bits.
 */
#define send_bits(s, value, length) \
{ int len = length;\
if (s->bi_valid > (int)Buf_size - len) {\
int val = value;\
s->bi_buf |= (val << s->bi_valid);\
put_short(s, s->bi_buf);\
s->bi_buf = (WORD)val >> (Buf_size - s->bi_valid);\
s->bi_valid += len - Buf_size;\
} else {\
s->bi_buf |= (value) << s->bi_valid;\
s->bi_valid += len;\
}\
}

/* the arguments must not have side effects */

/* ===========================================================================
 * Initialize the tree data structures for a new zlib stream.
 */

void _tr_init(deflate_state *s)
{
  s->l_desc.dyn_tree = s->dyn_ltree;
  s->l_desc.stat_desc = &static_l_desc;

  s->d_desc.dyn_tree = s->dyn_dtree;
  s->d_desc.stat_desc = &static_d_desc;

  s->bl_desc.dyn_tree = s->bl_tree;
  s->bl_desc.stat_desc = &static_bl_desc;

  s->bi_buf = 0;
  s->bi_valid = 0;
  s->last_eob_len = 8; /* enough lookahead for inflate */

  /* Initialize the first block of the first file: */
  init_block(s);
}

/* ===========================================================================
 * Initialize a new block.
 */
static void init_block(deflate_state *s)
{
  int n;

  for (n = 0; n < L_CODES; n++)
  {
    s->dyn_ltree[n].Freq = 0;
  }

  for (n = 0; n < D_CODES; n++)
  {
    s->dyn_dtree[n].Freq = 0;
  }

  for (n = 0; n < BL_CODES; n++)
  {
    s->bl_tree[n].Freq = 0;
  }

  s->dyn_ltree[END_BLOCK].Freq = 1;
  s->opt_len = s->static_len = 0L;
  s->last_lit = s->matches = 0;
}

//-------------------------------------------------------------------------

#define SMALLEST 1

/* ===========================================================================
 * Remove the smallest element from the heap and recreate the heap with
 * one less element. Updates heap and heap_len.
 */

#define pqremove(s, tree, top) \
{\
top = s->heap[SMALLEST]; \
s->heap[SMALLEST] = s->heap[s->heap_len--]; \
pqdownheap(s, tree, SMALLEST); \
}

/* ===========================================================================
 * Compares to subtrees, using the tree depth as tie breaker when
 * the subtrees have equal frequency. This minimizes the worst case length.
 */

#define smaller(tree, n, m, depth) \
(tree[n].Freq < tree[m].Freq || \
(tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))

/* ===========================================================================
 * Restore the heap property by moving down the tree starting at node k,
 * exchanging a node with the smallest of its two sons if necessary, stopping
 * when the heap property is re-established (each father smaller than its
 * two sons).
 */

static void pqdownheap(deflate_state *s, ct_data *tree, int k)
{
  int v = s->heap[k];
  int j = k << 1; /* left son of k */

  while (j <= s->heap_len)
  {
    /* Set j to the smallest of the two sons: */
    if (j < s->heap_len && smaller(tree, s->heap[j + 1], s->heap[j], s->depth))
    {
      j++;
    }

    /* Exit if v is smaller than both sons */
    if (smaller(tree, v, s->heap[j], s->depth))
    {
      break;
    }

    /* Exchange v with the smallest son */
    s->heap[k] = s->heap[j];
    k = j;

    /* And continue down the tree, setting j to the left son of k */
    j <<= 1;
  }
  s->heap[k] = v;
}

/* ===========================================================================
 * Compute the optimal bit lengths for a tree and update the total bit length
 * for the current block.
 * IN assertion: the fields freq and dad are set, heap[heap_max] and
 *    above are the tree nodes sorted by increasing frequency.
 * OUT assertions: the field len is set to the optimal bit length, the
 *     array bl_count contains the frequencies for each bit length.
 *     The length opt_len is updated; static_len is also updated if stree is
 *     not null.
 */

static void gen_bitlen(deflate_state *s, tree_desc *desc)
{
  ct_data *tree = desc->dyn_tree;
  int max_code = desc->max_code;
  const ct_data *stree = desc->stat_desc->static_tree;
  const intf *extra = desc->stat_desc->extra_bits;
  int base = desc->stat_desc->extra_base;
  int max_length = desc->stat_desc->max_length;
  int h; /* heap index */
  int n, m; /* iterate over the tree elements */
  int bits; /* bit length */
  int xbits; /* extra bits */
  WORD f; /* frequency */
  int overflow = 0; /* number of elements with bit length too large */

  for (bits = 0; bits <= MAX_BITS; bits++)
  {
    s->bl_count[bits] = 0;
  }

  /* In a first pass, compute the optimal bit lengths (which may
   * overflow in the case of the bit length tree).
   */
  tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */

  for (h = s->heap_max + 1; h < HEAP_SIZE; h++)
  {
    n = s->heap[h];
    bits = tree[tree[n].Dad].Len + 1;

    if (bits > max_length)
    {
      bits = max_length, overflow++;
    }

    tree[n].Len = (WORD)bits;
    /* We overwrite tree[n].Dad which is no longer needed */

    if (n > max_code)
    {
      continue;
    }
    /* not a leaf node */

    s->bl_count[bits]++;
    xbits = 0;

    if (n >= base)
    {
      xbits = extra[n - base];
    }
    f = tree[n].Freq;
    s->opt_len += (DWORD)f *(bits + xbits);

    if (stree)
    {
      s->static_len += (DWORD)f *(stree[n].Len + xbits);
    }
  }
  if (!overflow)
  {
    return ;
  }

  /* This happens for example on obj2 and pic of the Calgary corpus */

  /* Find the first bit length which could increase: */
  do
  {
    bits = max_length - 1;
    while (s->bl_count[bits] == 0)bits--;
    s->bl_count[bits]--; /* move one leaf down the tree */
    s->bl_count[bits + 1] += 2; /* move one overflow item as its brother */
    s->bl_count[max_length]--;
    /* The brother of the overflow item also moves one step up,
     * but this does not affect bl_count[max_length]
     */
    overflow -= 2;
  }
  while (overflow > 0)
    ;

  /* Now recompute all bit lengths, scanning in increasing frequency.
   * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all
   * lengths instead of fixing only the wrong ones. This idea is taken
   * from 'ar' written by Haruhiko Okumura.)
   */
  for (bits = max_length; bits != 0; bits--)
  {
    n = s->bl_count[bits];
    while (n != 0)
    {
      m = s->heap[--h];
      if (m > max_code)
      {
        continue;
      }
      if (tree[m].Len != (DWORD)bits)
      {
        s->opt_len += ((long)bits - (long)tree[m].Len)*(long)tree[m].Freq;
        tree[m].Len = (WORD)bits;
      }
      n--;
    }
  }
}

/* ===========================================================================
 * Generate the codes for a given tree and bit counts (which need not be
 * optimal).
 * IN assertion: the array bl_count contains the bit length statistics for
 * the given tree and the field len is set for all tree elements.
 * OUT assertion: the field code is set for all tree elements of non
 *     zero code length.
 */

static void gen_codes(ct_data *tree, int max_code, WORD *bl_count)
{
  WORD next_code[MAX_BITS + 1]; /* next code value for each bit length */
  WORD code = 0; /* running code value */
  int bits; /* bit index */
  int n; /* code index */

  /* The distribution counts are first used to generate the code values
   * without bit reversal.
   */
  for (bits = 1; bits <= MAX_BITS; bits++)
  {
    next_code[bits] = code = (code + bl_count[bits - 1]) << 1;
  }
  /* Check that the bit counts in bl_count are consistent. The last code
   * must be all ones.
   */

  for (n = 0; n <= max_code; n++)
  {
    int len = tree[n].Len;
    if (len == 0)
    {
      continue;
    }
    /* Now reverse the bits - DW */
    tree[n].Code = (WORD)bi_reverse(next_code[len]++, len);

  }
}

/* ===========================================================================
 * Construct one Huffman tree and assigns the code bit strings and lengths.
 * Update the total bit length for the current block.
 * IN assertion: the field freq is set for all tree elements.
 * OUT assertions: the fields len and code are set to the optimal bit length
 *     and corresponding code. The length opt_len is updated; static_len is
 *     also updated if stree is not null. The field max_code is set.
 */
static void build_tree(deflate_state *s, tree_desc *desc)
{
  ct_data *tree = desc->dyn_tree;
  const ct_data *stree = desc->stat_desc->static_tree;
  int elems = desc->stat_desc->elems;
  int n, m; /* iterate over heap elements */
  int max_code =  - 1; /* largest code with non zero frequency */
  int node; /* new node being created */

  /* Construct the initial heap, with least frequent element in
   * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
   * heap[0] is not used.
   */
  s->heap_len = 0, s->heap_max = HEAP_SIZE;

  for (n = 0; n < elems; n++)
  {
    if (tree[n].Freq != 0)
    {
      s->heap[++(s->heap_len)] = max_code = n;
      s->depth[n] = 0;
    }
    else
    {
      tree[n].Len = 0;
    }
  }

  /* The pkzip format requires that at least one distance code exists,
   * and that at least one bit should be sent even if there is only one
   * possible code. So to avoid special checks later on we force at least
   * two codes of non zero frequency.
   */
  while (s->heap_len < 2)
  {
    node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code: 0);
    tree[node].Freq = 1;
    s->depth[node] = 0;
    s->opt_len--;

    if (stree)
    {
      s->static_len -= stree[node].Len;
    }
    /* node is 0 or 1 so it does not have extra bits */
  }
  desc->max_code = max_code;

  /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
   * establish sub-heaps of increasing lengths:
   */
  for (n = s->heap_len / 2; n >= 1; n--)
  {
    pqdownheap(s, tree, n);
  }

  /* Construct the Huffman tree by repeatedly combining the least two
   * frequent nodes.
   */
  node = elems; /* next internal node of the tree */

  do
  {
    pqremove(s, tree, n); /* n = node of least frequency */
    m = s->heap[SMALLEST]; /* m = node of next least frequency */

    s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */
    s->heap[--(s->heap_max)] = m;

    /* Create a new node father of n and m */
    tree[node].Freq = tree[n].Freq + tree[m].Freq;
    s->depth[node] = (BYTE)((s->depth[n] >= s->depth[m] ? s->depth[n]: s->depth[m]) + 1);
    tree[n].Dad = tree[m].Dad = (WORD)node;
    #ifdef DUMP_BL_TREE
      if (tree == s->bl_tree)
      {
        fprintf(stderr, "\nnode %d(%d), sons %d(%d) %d(%d)", node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);
      }
    #endif
    /* and insert the new node in the heap */
    s->heap[SMALLEST] = node++;
    pqdownheap(s, tree, SMALLEST);

  }
  while (s->heap_len >= 2);

  s->heap[--(s->heap_max)] = s->heap[SMALLEST];  

  /* At this point, the fields freq and dad are set. We can now
   * generate the bit lengths.
   */
  gen_bitlen(s, (tree_desc*)desc);

  /* The field len is now set, we can generate the bit codes */
  gen_codes((ct_data*)tree, max_code, s->bl_count);
}

/* ===========================================================================
 * Scan a literal or distance tree to determine the frequencies of the codes
 * in the bit length tree.
 */
static void scan_tree(deflate_state *s, ct_data *tree, int max_code)
{
  int n; /* iterates over all tree elements */
  int prevlen =  - 1; /* last emitted length */
  int curlen; /* length of current code */
  int nextlen = tree[0].Len; /* length of next code */
  int count = 0; /* repeat count of the current code */
  int max_count = 7; /* max repeat count */
  int min_count = 4; /* min repeat count */

  if (nextlen == 0)
  {
    max_count = 138, min_count = 3;
  }
  tree[max_code + 1].Len = (WORD)0xffff; /* guard */

  for (n = 0; n <= max_code; n++)
  {
    curlen = nextlen;
    nextlen = tree[n + 1].Len;
    if (++count < max_count && curlen == nextlen)
    {
      continue;
    }
    else if (count < min_count)
    {
      s->bl_tree[curlen].Freq += count;
    }
    else if (curlen != 0)
    {
      if (curlen != prevlen)
      {
        s->bl_tree[curlen].Freq++;
      }
      s->bl_tree[REP_3_6].Freq++;
    }
    else if (count <= 10)
    {
      s->bl_tree[REPZ_3_10].Freq++;
    }
    else
    {
      s->bl_tree[REPZ_11_138].Freq++;
    }
    count = 0;
    prevlen = curlen;
    if (nextlen == 0)
    {
      max_count = 138, min_count = 3;
    }
    else if (curlen == nextlen)
    {
      max_count = 6, min_count = 3;
    }
    else
    {
      max_count = 7, min_count = 4;
    }
  }
}

/* ===========================================================================
 * Send a literal or distance tree in compressed form, using the codes in
 * bl_tree.
 */
static void send_tree(deflate_state *s, ct_data *tree, int max_code)
{
  int n; /* iterates over all tree elements */
  int prevlen =  - 1; /* last emitted length */
  int curlen; /* length of current code */
  int nextlen = tree[0].Len; /* length of next code */
  int count = 0; /* repeat count of the current code */
  int max_count = 7; /* max repeat count */
  int min_count = 4; /* min repeat count */

   /* tree[max_code+1].Len = -1; */ /* guard already set */
  if (nextlen == 0)
  {
    max_count = 138, min_count = 3;
  }

  for (n = 0; n <= max_code; n++)
  {
    curlen = nextlen;
    nextlen = tree[n + 1].Len;
    if (++count < max_count && curlen == nextlen)
    {
      continue;
    }
    else if (count < min_count)
    {
      do
      {
        send_code(s, curlen, s->bl_tree);
      }
      while (--count != 0);

    }
    else if (curlen != 0)
    {
      if (curlen != prevlen)
      {
        send_code(s, curlen, s->bl_tree);
        count--;
      }
      send_code(s, REP_3_6, s->bl_tree);
      send_bits(s, count - 3, 2);

    }
    else if (count <= 10)
    {
      send_code(s, REPZ_3_10, s->bl_tree);
      send_bits(s, count - 3, 3);

    }
    else
    {
      send_code(s, REPZ_11_138, s->bl_tree);
      send_bits(s, count - 11, 7);
    }
    count = 0;
    prevlen = curlen;
    if (nextlen == 0)
    {
      max_count = 138, min_count = 3;
    }
    else if (curlen == nextlen)
    {
      max_count = 6, min_count = 3;
    }
    else
    {
      max_count = 7, min_count = 4;
    }
  }
}

/* ===========================================================================
 * Construct the Huffman tree for the bit lengths and return the index in
 * bl_order of the last bit length code to send.
 */
static int build_bl_tree(deflate_state *s)
{
  int max_blindex; /* index of last bit length code of non zero freq */

  /* Determine the bit length frequencies for literal and distance trees */
  scan_tree(s, (ct_data*)s->dyn_ltree, s->l_desc.max_code);
  scan_tree(s, (ct_data*)s->dyn_dtree, s->d_desc.max_code);

  /* Build the bit length tree: */
  build_tree(s, (tree_desc*)(&(s->bl_desc)));
  /* opt_len now includes the length of the tree representations, except
   * the lengths of the bit lengths codes and the 5+5+4 bits for the counts.
   */

  /* Determine the number of bit length codes to send. The pkzip format
   * requires that at least 4 bit length codes be sent. (appnote.txt says
   * 3 but the actual value used is 4.)
   */
  for (max_blindex = BL_CODES - 1; max_blindex >= 3; max_blindex--)
  {
    if (s->bl_tree[bl_order[max_blindex]].Len != 0)
    {
      break;
    }
  }
  /* Update opt_len to include the bit length tree and counts */
  s->opt_len += 3 *(max_blindex + 1) + 5+5+4;

  return max_blindex;
}

/* ===========================================================================
 * Send the header for a block using dynamic Huffman trees: the counts, the
 * lengths of the bit length codes, the literal tree and the distance tree.
 * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.
 */
static void send_all_trees(deflate_state *s, int lcodes, int dcodes, int blcodes)
{
  int rank; /* index in bl_order */

  send_bits(s, lcodes - 257, 5); /* not +255 as stated in appnote.txt */
  send_bits(s, dcodes - 1, 5);
  send_bits(s, blcodes - 4, 4); /* not -3 as stated in appnote.txt */
  for (rank = 0; rank < blcodes; rank++)
  {
    send_bits(s, s->bl_tree[bl_order[rank]].Len, 3);
  }
  send_tree(s, (ct_data*)s->dyn_ltree, lcodes - 1); /* literal tree */
  send_tree(s, (ct_data*)s->dyn_dtree, dcodes - 1); /* distance tree */
}

/* ===========================================================================
 * Send a stored block
 */
void _tr_stored_block(deflate_state *s, BYTE *buf, DWORD stored_len, int eof)
{
  send_bits(s, (STORED_BLOCK << 1) + eof, 3); /* send block type */
  copy_block(s, buf, (DWORD)stored_len, 1); /* with header */
}

/* ===========================================================================
 * Send one empty static block to give enough lookahead for inflate.
 * This takes 10 bits, of which 7 may remain in the bit buffer.
 * The current inflate code requires 9 bits of lookahead. If the
 * last two codes for the previous block (real code plus EOB) were coded
 * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode
 * the last real code. In this case we send two empty static blocks instead
 * of one. (There are no problems if the previous block is stored or fixed.)
 * To simplify the code, we assume the worst case of last real code encoded
 * on one bit only.
 */
void _tr_align(deflate_state *s)
{
  send_bits(s, STATIC_TREES << 1, 3);
  send_code(s, END_BLOCK, static_ltree);

  bi_flush(s);
  /* Of the 10 bits for the empty block, we have already sent
   * (10 - bi_valid) bits. The lookahead for the last real code (before
   * the EOB of the previous block) was thus at least one plus the length
   * of the EOB plus what we have just sent of the empty static block.
   */
  if (1+s->last_eob_len + 10-s->bi_valid < 9)
  {
    send_bits(s, STATIC_TREES << 1, 3);
    send_code(s, END_BLOCK, static_ltree);

    bi_flush(s);
  }

  s->last_eob_len = 7;
}

/* ===========================================================================
 * Determine the best encoding for the current block: dynamic trees, static
 * trees or store, and output the encoded block to the zip file.
 */
void _tr_flush_block(deflate_state *s, BYTE *buf, DWORD stored_len, int eof)
{
  DWORD opt_lenb, static_lenb; /* opt_len and static_len in bytes */
  int max_blindex = 0; /* index of last bit length code of non zero freq */

  /* Build the Huffman trees unless a stored block is forced */
  if (s->level > 0)
  {
    /* Check if the file is ascii or binary */
    if (s->data_type == Z_UNKNOWN)
    {
      set_data_type(s);
    }

    /* Construct the literal and distance trees */
    build_tree(s, (tree_desc*)(&(s->l_desc)));
    build_tree(s, (tree_desc*)(&(s->d_desc)));
    /* At this point, opt_len and static_len are the total bit lengths of
     * the compressed block data, excluding the tree representations.
     */

    /* Build the bit length tree for the above two trees, and get the index
     * in bl_order of the last bit length code to send.
     */
    max_blindex = build_bl_tree(s);

    /* Determine the best encoding. Compute the block lengths in bytes. */
    opt_lenb = (s->opt_len + 3+7) >> 3;
    static_lenb = (s->static_len + 3+7) >> 3;

    if (static_lenb <= opt_lenb)
    {
      opt_lenb = static_lenb;
    }

  }
  else
  {
    opt_lenb = static_lenb = stored_len + 5; /* force a stored block */
  }

  #ifdef FORCE_STORED
    if (buf != (char*)0)
    {
      /* force stored block */
    #else
      if (stored_len + 4 <= opt_lenb && buf != (char*)0)
      {
        /* 4: two words for the lengths */
      #endif
      /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.
       * Otherwise we can't have processed more than WSIZE input bytes since
       * the last block flush, because compression would have been
       * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to
       * transform a block into a stored block.
       */
      _tr_stored_block(s, buf, stored_len, eof);

      #ifdef FORCE_STATIC
      }
      else if (static_lenb >= 0)
      {
        /* force static trees */
      #else
      }
      else if (static_lenb == opt_lenb)
      {
      #endif
      send_bits(s, (STATIC_TREES << 1) + eof, 3);
      compress_block(s, (ct_data*)static_ltree, (ct_data*)static_dtree);
    }
    else
    {
      send_bits(s, (DYN_TREES << 1) + eof, 3);
      send_all_trees(s, s->l_desc.max_code + 1, s->d_desc.max_code + 1, max_blindex + 1);
      compress_block(s, (ct_data*)s->dyn_ltree, (ct_data*)s->dyn_dtree);
    }
    /* The above check is made mod 2^32, for files larger than 512 MB
     * and uLong implemented on 32 bits.
     */
    init_block(s);

    if (eof)
    {
      bi_windup(s);
    }
  }

  /* ===========================================================================
   * Save the match info and tally the frequency counts. Return true if
   * the current block must be flushed.
   */
  int _tr_tally(s, dist, lc)deflate_state *s;
  DWORD dist; /* distance of matched string */
  DWORD lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */
  {
    s->d_buf[s->last_lit] = (WORD)dist;
    s->l_buf[s->last_lit++] = (BYTE)lc;
    if (dist == 0)
    {
      /* lc is the unmatched char */
      s->dyn_ltree[lc].Freq++;
    }
    else
    {
      s->matches++;
      /* Here, lc is the match length - MIN_MATCH */
      dist--; /* dist = match distance - 1 */
      s->dyn_ltree[_length_code[lc] + LITERALS + 1].Freq++;
      s->dyn_dtree[d_code(dist)].Freq++;
    }

    #ifdef TRUNCATE_BLOCK
      /* Try to guess if it is profitable to stop the current block here */
      if ((s->last_lit &0x1fff) == 0 && s->level > 2)
      {
        /* Compute an upper bound for the compressed length */
        ulg out_length = (ulg)s->last_lit *8L;
        ulg in_length = (ulg)((long)s->strstart - s->block_start);
        int dcode;
        for (dcode = 0; dcode < D_CODES; dcode++)
        {
          out_length += (ulg)s->dyn_dtree[dcode].Freq *(5L + extra_dbits[dcode]);
        }
        out_length >>= 3;
        Tracev((stderr, "\nlast_lit %u, in %ld, out ~%ld(%ld%%) ", s->last_lit, in_length, out_length, 100L - out_length * 100L / in_length));
        if (s->matches < s->last_lit / 2 && out_length < in_length / 2)
        {
          return 1;
        }
      }
    #endif
    return (s->last_lit == s->lit_bufsize - 1);
    /* We avoid equality with lit_bufsize because of wraparound at 64K
     * on 16 bit machines and because stored blocks are restricted to
     * 64K-1 bytes.
     */
  }

  /* ===========================================================================
   * Send the block data compressed using the given Huffman trees
   */
  static void compress_block(deflate_state *s, ct_data *ltree, ct_data *dtree)
  {
    DWORD dist; /* distance of matched string */
    int lc; /* match length or unmatched char (if dist == 0) */
    DWORD lx = 0; /* running index in l_buf */
    DWORD code; /* the code to send */
    int extra; /* number of extra bits to send */

    if (s->last_lit != 0)
    {
      do
      {
        dist = s->d_buf[lx];
        lc = s->l_buf[lx++];
        if (dist == 0)
        {
          send_code(s, lc, ltree); /* send a literal byte */
        }
        else
        {
          /* Here, lc is the match length - MIN_MATCH */
          code = _length_code[lc];
          send_code(s, code + LITERALS + 1, ltree); /* send the length code */
          extra = extra_lbits[code];
          if (extra != 0)
          {
            lc -= base_length[code];
            send_bits(s, lc, extra); /* send the extra length bits */
          }
          dist--; /* dist is now the match distance - 1 */
          code = d_code(dist);
          send_code(s, code, dtree); /* send the distance code */
          extra = extra_dbits[code];

          if (extra != 0)
          {
            dist -= base_dist[code];
            send_bits(s, dist, extra); /* send the extra distance bits */
          }
        } /* literal or match pair ? */

        /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
      }
      while (lx < s->last_lit);
    }

    send_code(s, END_BLOCK, ltree)
      ;
    s->last_eob_len = ltree[END_BLOCK].Len;
  }

  /* ===========================================================================
   * Set the data type to ASCII or BINARY, using a crude approximation:
   * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise.
   * IN assertion: the fields freq of dyn_ltree are set and the total of all
   * frequencies does not exceed 64K (to fit in an int on 16 bit machines).
   */
  static void set_data_type(deflate_state *s)
  {
    int n = 0;
    DWORD ascii_freq = 0;
    DWORD bin_freq = 0;

    while (n < 7)
    {
      bin_freq += s->dyn_ltree[n++].Freq;
    }
    while (n < 128)
    {
      ascii_freq += s->dyn_ltree[n++].Freq;
    }
    while (n < LITERALS)
    {
      bin_freq += s->dyn_ltree[n++].Freq;
    }
    s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII);
  }

  /* ===========================================================================
   * Reverse the first len bits of a code, using straightforward code (a faster
   * method would use a table)
   * IN assertion: 1 <= len <= 15
   */
  static DWORD bi_reverse(DWORD code, int len)
  {
    register DWORD res = 0;

    do
    {
      res |= code &1;
      code >>= 1, res <<= 1;
    }
    while (--len > 0);

    return res >> 1;
  }

  /* ===========================================================================
   * Flush the bit buffer, keeping at most 7 bits in it.
   */
  static void bi_flush(deflate_state *s)
  {
    if (s->bi_valid == 16)
    {
      put_short(s, s->bi_buf);
      s->bi_buf = 0;
      s->bi_valid = 0;
    }
    else if (s->bi_valid >= 8)
    {
      put_byte(s, (Byte)s->bi_buf);
      s->bi_buf >>= 8;
      s->bi_valid -= 8;
    }
  }

  /* ===========================================================================
   * Flush the bit buffer and align the output on a byte boundary
   */
  static void bi_windup(deflate_state *s)
  {
    if (s->bi_valid > 8)
    {
      put_short(s, s->bi_buf);
    }
    else if (s->bi_valid > 0)
    {
      put_byte(s, (Byte)s->bi_buf);
    }
    s->bi_buf = 0;
    s->bi_valid = 0;
  }

  /* ===========================================================================
   * Copy a stored block, storing first the length and its
   * one's complement if requested.
   */
  static void copy_block(deflate_state *s, BYTE *buf, DWORD len, int header)
  {
    bi_windup(s); /* align on byte boundary */
    s->last_eob_len = 8; /* enough lookahead for inflate */

    if (header)
    {
      put_short(s, (WORD)len);
      put_short(s, (WORD)~len);

    }

    while (len--)
    {
      put_byte(s,  *buf++);
    }
  }
